Electric discharge device



M y 1951 J. MCI. FERGUSON ELECTRIC mscmmcs DEVICE Filed March 25, 1950 INVENTORS ATTORNEYS JOHN M.FERGUSON REGINALD D. BALL Y Bafiwu $6M Patented May 29, i951 ELECTRIC DISCHARGE DEVICE John McIntyre Ferguson and Reginald Donahoe Ball, Stafford, England, assignors to The English Electric Company Limited, London, England, a British company Application March 23, 1950, Serial No. 151,396 In Great Britain April 6, 1949 Thi invention relates to electric discharge devices of the kind havin a liquid vpool cathode. Such devices have in the past been unsuitable for use in transportation applications such as in ships, trains and aircraft since the cathode liquid has been kept in position by gravity and any sudden acceleration of the devices other than in an upward direction normal to the surface of the cathode pool would result in displacement of the cathode material and might interfere with the operation of the device. Attempts have been made to overcome this difficulty by the use of gimbal mountings for the devices but such an arrangement is only suitable for use where the acceleration is small and if, as in transportation applications, accelerations are imposed, for example, of the order of several times gi (acceleration due to gravity) the device may fail.

According to the invention, in an electric discharge device having a liquid pool cathode means are provided to cause the material of said cathode to revolve whereby it is retained in a cathode region by centrifugal force against the effects of accelerational forces applied to the device.

According to a further feature of the invention rotation is imparted to the cathode material by arranging to rotate the envelope of the device. Paddles may be provided fixed to the interior of the envelope to assist in imparting rotation to the liquid cathode material.

In cases where the envelope of the device is rotated to impart rotation to the cathode material, it is necessary that the internal configuration of the envelope should be such that the centrifugal force applied to cathode material condensed on the envelope in any region other than the cathode region should either assist in returning the condensed material to the cathode region or should be insufiicient to prevent its return by gravity.

By way of example one form of the invention is shown in the accompanying drawing applied to a single phase full wave grid controlled mercury arc rectifier. An envelope I, which may be of vitreous or ceramic material has the general form of two cones arranged base to base, the medial portion having the form of an annular groove and constitutinga cathode region to accommodate a pool of mercury 2. The envelope 1 may be provided in the cathode region with paddles 3. An annular electrode 4 is arranged in the cathode region and is connected by leadin conductors to an external collector ring 5 upon 9 Claims. (Cl. 2502'7.5)

which brushes 5 are arranged to operate. Annular striking electrodes la and lb are arranged within the envelope on either side of the cathode region and are similarly connected by means of lead-in conductors to further collector rings 8a and 8b with which brushes 9a and 9b co-operate. A pair of grids Ida and lb is provided in order to control the output voltage of the device and these are again connected by lead-in conductors to collector rings Ma and l lb with which brushes in and I 2b co-operate. Anodes |3a and |3b are located in the two ends of the envelope and these are connected to sliprings Ma and Nb each with associated brushes l5a and I517. The envelope is mounted for rotation on shaft 56 extending axially from the sliprings 14a and Mb and mounted in bearings I! carried on insulating pillars IS. A further bearing I9 may be provided to support the envelope medially. One of the shafts I6 is provided with an insulating coupling 20 and is driven by an electric motor '21. One or more fans 22 may also be provided for cooling the device and the whole assembly may be mounted within a tubular duct 23. When the rectifier is at rest, the cathode material will lie in the lower portion of the envelope I and its surface will occupy a position, indicated by the dotted line 24, in which it is in contact with the two striking electrodes la and 11). A voltage is applied to the two striking electrodes and on rotation of the rectifier by the motor 2! the axial width of the mercury decreases as it increases in speed until the circuit between the striking electrodes is broken and an arc is set up which is then maintained in the usual manner.

It will be seen that whatever the position of the envelope l in space, on rotation, the mercury will always assume the largest possible radius and kinetic energy and will therefore remain in the cathode region. Owing to the sharply inclined surface of the envelope in this region the centrifugal force applied to the mercury will tend to prevent its leaving the cathode region upon the incidence of accelerational forces. applied axially of the device. 'As is well known, the centrifugal force may be expressed as 1.22 (revs. per sec.) radius in feet. Thus, for example, in a rectifier havinga maximum internal radius of 6" and rotating at only 600 R. P. M., the centrifugal force applied to the mercury will be 6l the force due to g.

The power supplied by the motor 2| need only be sufficient to overcome the bearing friction,-

windage and brush friction at the desired speed of operation.

It will be understood that with small rectifiers the natural windage may sullice for cooling and that the fans 22 and/or the duct 23 may be omitted in suitable cases.

Whilst a double ended rectifier has been shown, it will be obvious that a single ended rectifier can be constructed in exactly the same way, with that portion of the device to the left of the dotted line AA in the drawing omitted and the envelope blanked oiT in the region of that line. It will further be obvious that for polyphase operation a rectifier according to the invention can be made having, for example, three anodes at each end with three grids, in the place of the single anode and single grid at each end. The spacing of these grids and anodes would be at 120 in order to ensure balance and a corresponding number of collector rings and brushes would, of course, be provided.

While the invention has been described in relation to a rectifier, it will be appreciated that it is equally applicable to other forms of pool cathode discharged devices such as converters.

What we claim as our invention and desire to secure by Letters Patent is:

1. An electric discharge device having an envelope, a liquid pool cathode within said envelope, a portion of said envelope defining a cathode region, and means for rotating said envelope, the

cathode region being further from the axis of rotation than any other region within the envelope of the device, and the walls of the envelope between the cathode region and the region nearest the axis of rotation being so shaped that condensed cathode material is returned by centrifugal force to the cathode region.

2. An electric discharge device having an envelope, a liquid pool cathode within said envelope, a portion of said envelope defining a cathode region, and means for rotating said envelope, the cathode region being further from the axis of rotation than any other region within the envelope of the device, and the walls of the envelope between the cathode region and the region nearest the axis of rotation being of substantially conical formation tapering away from said cathode region.

3. An electric discharge device having an envelope. a liquid pool cathode within said envelope, a portion of said envelope defining a cathode region, means for rotating said envelope, and paddle means attached to said envelope in said cathode region, the cathode region being further from the axis of rotation than any other region within the envelope of the device, and the Walls of the envelope between the cathode region and the region nearest the axis of rotation being so shaped that condensed cathode material is returned by centrifugal force to the cathode region.

4. An electric discharge device comprising a rotatable envelope having a generall conical main portion with its axis on the axis of rotation, a cathode region at the base of said main portion and joined thereto by a wall portion which makes a less acute angle to the axis of rotation than does the wall of the main portion of the envelope, a body of liquid cathode material adapted to form a cathode in said cathode region, an anode in said main portion of the envelope, and brush means for leading current to and from each of the electrodes.

5. An electric discharge device comprising a rotatable envelope having a generally conical main portion with its axis on the axis of rotation, a cathode region at the base of said main portion and joined thereto by a wall portion which makes a less acute angle to the axis of rotation than does the wall of the main portion of the envelope, a body of liquid cathode material adapted to form a cathode in said cathode region, an anode in said main portion of the envelope, a control electrode between said cathode and said anode, and brush means for leading current to and from each of the electrodes.

6. An electric discharge device comprising a rotatable envelope having a generally conical main portion with its axis on the axis of rotation, a cathode region at the base Of said main portion and joined thereto by a Wall portion which makes a less acute angle to the axis of rotation than does the Wall of the main portion of the envelope, a body of liquid cathode material adapted to form a cathode in said cathode region, an anode in said main portion of the envelope, a control electrode between said cathode and said anode, an annular starting electrode positioned so that it may be in contact with the material of the cathode when the device is not being rotated and so that it is out of contact with the material of the cathode on rotation of the device, and brush means for leading current to and from each of the electrodes.

'7. An electric discharge device having an envelope, a liquid p001 cathode within said envelope, a portion of said envelope defining a cathode region and means for causing the material of said cathode to revolve in the cathode region so as to be retained therein against the effects of accelerational forces applied to the device.

8. A rotatable double anode grid controlled rectifier device comprising two main generally conical portions, base to base, an annular cathode region between said conical portions and of greater diameter than the maximum diameter of said conical portions, an anode near the apex of each conical portion, a control electrode between each anode and said cathode, an annular starting electrode in each conical portion each positioned so that it may be in contact with the material of the cathode when the device is not being rotated and so that it is out of contact with the material of the cathode on rotation of the device, and brush means for leading current to and from each of the electrodes.

9. A rotatable double anode grid controlled rectifier device comprising two main generally conical portions base to base, an annular cathode region between said conical portions and of greater diameter than the maximum diameter of said conical portions, an anode near the apex of each conical portion, a control electrode between each anode and said cathode, an annular starting electrode in each conical portion each positioned so that it may be in contact with the material of the cathode when the device is not being rotated and so that it is out of contact with the material of the cathode on rotation of the device, brush means for leading current to and from each of the electrodes, an electric motor in operative relation with said rectifier for rotating the same, a fan driven by said electric motor, and a tubular housing for said rectifier, said motor and said fan.

JOHN McINTYRE FERGUSON. REGINALD DONAI-IOE BALL.

- No references cited. 

